No, I don't want to sort them by "published date" but by "creation date". Sorting by "published" sorts nodes based on creation date of the last published version. But I wan't to sort them by the creation date of the object, that is the creation date of the first version that was created. Is this possible somehow?
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Nothing is impossible. Not if you can imagine it!
The published date only is initialized when the object gets published for the first time (it's still 0). The modified time is changed every time a new version is published.
See kernel/content/ezcontentoperationcollection.php function setObjectStatusPublished, starting from line 184 on trunk rev. 16527